A pneumatic tyre may be used in various types of vehicles and automobiles. A pneumatic tyre, once mounted on a rim and inflated, is capable to absorb shocks when moving over uneven road. An inflated pneumatic tyre mounted under a vehicle thus serves as an inflatable cushioning for a vehicle.
Approximately close to a billion pneumatic tyres are manufactured annually in the world. A pneumatic tyre typically comprises a variety of different materials, such as rubber based components. Rubber based components typically join various tyre materials together, when the tyre is cured during the tyre manufacturing process. A rubber based component of a pneumatic tyre typically comprises natural rubber and/or synthetic rubber. The rubber is typically mixed with carbon black in order to obtain rubber having higher reinforcement characteristics.
Each tyre component can be designed for a dedicated purpose. For example, tread area components of a pneumatic tyre, which typically are in contact with the road, may require different characteristics than non-tread area components of the tyre. The composition of the rubber based component therefore plays a role in the viscoelastic and mechanical performance of the tyre. The amount and type of materials used in the composition of the rubber based component may have an effect e.g. on traction, tread wear and rolling resistance of the tyre.
Rolling resistance refers to deformation of the tyre, when the tyre is rotating and is in contact with the road surface. The resistance is to a large extent due to the viscoelastic behavior of the tyre. Rolling resistance accounts for a considerable proportion of fuel consumption in fuel-driven vehicles. Rolling resistance also plays a role in the energy consumption of other types of vehicles, such as those using hybrid technologies or electricity. Traction and tread wear are performance parameters which also affect the behavior and durability of the tyre. While traction is typically desirable, the tread wear and rolling resistance of the tyre are not desirable. The tyre performance optimization thus form a challenge, since the optimization of one parameter often may lead to negative results in other desired characteristics.
Tyre characteristics such as durability, reinforcing effect or viscoelastic behavior, are related to the proportion of filler materials in the rubber based components, such as carbon black. A pneumatic tyre may comprise high amounts of carbon black as reinforcing filler material, such as up to 40 wt. % or more. One of the most common uses of carbon black nowadays is as a pigment and reinforcing filler material in automobile tyres. Carbon black consists mostly of elemental carbon. Carbon black is typically manufactured from fossile carbon sources. Rubber-grade carbon black is typically manufactured in specific grades, each grade having defined characteristics, such as size distribution and specific surface area according to ASTM standard D1765-14. The final characteristics of a tyre are determined from a cured tyre. Curing is typically done by vulcanization means.
Rolling resistance may be reduced by adding inorganic filler material, such as silica, into the rubber based components located on the tread area of the tyre. Silica (SiO2) is a chemical compound, which exists in various grades and forms, for example as precipitated silica.
Conventional filler materials such as carbon black and silica, when used as such, are relatively inert. Carbon black interacts in the rubber based component mainly by means of physical interactions. Silica on the other hand, only interacts once bound into the tyre component by means of a silane based coupling agent.
Conventional tyre materials pose many challenges. Tyre manufacturing industry is a major consumer of materials used in rubber based components. A pneumatic tyre may comprise equal to or more than 80 wt. % of rubber based components, when calculated of the total weight of the tyre. The extensive use of material originating from fossile carbon sources in a tyre is a problem. The complex material composition of traditional tyres makes them difficult to recycle. The tyre rubber manufacturing process may involve the use of hazardous material, for example to increase stiffness of the rubber component. Silica is relatively expensive. Despite of the use of silica, the conventional filler materials still cause considerable amounts of heat generation and flexing fatigue of a tyre, when the tyre is used, which is undesirable.
Rapidly emerging environmental aspects, such as fuel consumption and noise level reduction efforts in the automobile industry, set new requirements also to tyre manufacturers. The renewability requirements and environmental aspects of a tyre play an increasingly important role in the selection of tyre raw materials. There is a need to produce tyres having improved performance characteristics and better environmental sustainability.